47Bell 47

Parts most often named Grip (6) · Hub (3) · Yoke (2) · Nut (2)

DURING LOW LEVEL CROP APPLICATION, PILOT HEARD A LOUD POP FOLLOWED BY VIBRATION, LANDED ACFT. NOTICED A CRACK IN THE UNDERSIDE OF THE GRIP DURING A VISUAL INSPECTION. CRACK WAS APPROX 70 PERCENT ACROSS THE LOWER EAR AT THE MAIN ROTOR BLADE BOLT HOLE.

PART WAS INSTALLED. ON REVIEW OF AIRCRAFT RECORDS PRIOR TO PLACING IT ON A 135 CERTIFICATE IT WAS NOTED THAT EITHER THERE WAS A TYPO OR SUP PART INSTALLED ON THE AIRCRAFT. THE FSDO CONFIRMED THE [S/N removed] ON SEPTEMBER 2, 2008 AFTER THE MAIN ROTOR WAS REMOVED REVEALING THE [S/N removed]. MANUFACTURER CONFRMED THE [S/N removed] WAS NOT A MANUFACTURER [S/N removed].

PART WAS TO REPLACE ANOTHER PART NOW IDENTIFIED AS A SUSPECTED UNAPPROVED PART (SUP). [S/N removed] CT-207 DOES NOT MEET THE REQUIREMENTS OF AN APPROVED PART: INCOMPLETE PAPERWORK, IDENTIFICATION MARKINGS, AND QUESTIONABLE INDICATION OF MANUFACTURE HISTORY. THE FSDO CONTACTED THE MANUFACTURER SUSPECTED UNAPPROVED PARTS DIVISION AND COULD NOT ESTABLISH THAT CT-207 IS A PART MANUFACTURED BY THEM.

Parts most often named Bearing (7) · Spider Set (2) · Drive (1) · Bearing Cage (1)

(CAN) DURING ROUTINE INSPECTION, SMALL AMOUNT OF BRASS WAS FOUND IN OIL SCREEN, THE TRANSMISSION WAS DISASSEMBLED TO LOCATE THE FAILED ITEM AND IT WAS FOUND TO BE ONE OF THE BEARING CAGES IN THE DUPLEX BEARING THAT THE UPPER SUN GEAR GOES THROUGH, THIS IS THE NEW AND IMPROVED BEARING INSTALLED IAW TB 47-75-4 (TC NR 20071102013)

UPON FINDING METAL IN OIL SCREEN, TRANSMISSION WAS REMOVED AND DISASSEMBLED. LOWER SUN GEAR BEARING WAS FOUND TO BE MAKING METAL. SUBMITTER STATES THIS HAS BEEN THE SIXTH FAILURE IN TRANSMISSION.

OPERATOR REPORTS 5 TRANSMISSION BEARING FAILURES WITHIN THE LAST YEAR. SUSPECT IMPROPERLY MANUFACTURED BEARINGS, AND, AS A RESULT, IMPROPER INSTALLATION. AN ACCIDENT PREVENTION RECOMMENDATION WAS SUBMITTED TO AAI-200.

Parts most often named Blade (5) · Pitch Horn (1) · Grip (1)

THE STAINLESS STEEL ABRASION STRIP ON THE LEADING EDGE OF THE COMPOSITE TAIL ROTOR BLADE SEPARATED FROM BLADE IN FLIGHT. PILOT NOTED A VIBRATION IN A SPRAY TURN AND ELECTED TO LAND; AND LANDED SAFELY (NO INJURIES).

DURING ACCIDENT INVESTIGATION, FOUND EVIDENCE OF FATIGUE FRACTURE ON TAIL ROTOR BLADE. OPPOSING BLADE WAS FRACTURED DUE TO APPARENT OVERLOAD. BOTH BLADES SENT TO MFG LABS UNDER NTSB ESCORT. TEARDOWN REPORT INDICATES BOTH BLADES HAD PROGRESSIVE FATIGUE EMANATING FROM PITTING OF INTERNAL BLADE SKINS. PITTING TRACED TO PREBONDING ETCHING PROCESS DURING MFG. MFG LABS REPORT THIS CONDITION BEING INVESTIGATED FOR OTHER BLADES MANUFACTURED AROUND THE SAME DATES. NO FINAL ANALYSIS AVAILABLE. (K)

CRACK LIKE INDICATION ON 9TH THREAD INBOARD WHICH EXCEEDS 15 PERCENT. IAW AD. PART REJECTED AND RED TAGGED BY REPAIR STATION. OPERATOR STATED PART WAS PURCHASED AS SPARE PRIOR TO AD. PART DESTROYED BY OPERATOR.

Parts most often named Cooling Fan (2) · Gear Set (1) · Sleeve (1) · Shaft (1)

APPROX 100 HRS AGO TRANSMISSION WAS O/H AND NEW PMA GEAR SET WAS INSTALLED [S/N removed] FROM HELICOPTER TECH DURING FLIGHT PILOT HEARD AND FELT NOISE AND MADE A PRECAUTIONARY LANDING AND FOUND COOLING FAN DRIVE PULLEY AND APPROX 1.25 INCHES OF THE DRIVE SHAFT WAS MISSING. WE ARE SENDING IN REMAINING SHAFT SEGMENT WHERE IT SHEARED FOR METALLURGICAL ANALYSIS.

(AUS) COOLING FAN MOUNT STUD LOCATED ON CRANKCASE FAILED. LOSS OF TENSION ALLOWED BELT TO FALL OFF AND DESTROY THE COOLING FAN.

(AUS) MAIN TRANSMISSION FAN PULLEY ASSEMBLY GEARSHAFT SPLINES WORN. SEE OPERATOR CONTROL NR AU981525 FOR ADDITIONAL INFORMATION.

Parts most often named Guide (1) · Piston (1) · Cover (1) · Cylinder (1)

A PUNCTURE WAS NOTICED ON THE INTAKE SIDE OF THE ROCKER COVER ON CYLINDER NR 1. UPON REMOVAL OF THE ROCKER COVER, A CAP PN 17C19386 WHICH SITS BETWEEN THE EXHAUST VALVE AND EXHAUST ROCKER ARM, WAS FOUND LODGED BETWEEN THE INTAKE COVER AND INTAKE ROCKER ARM. UPON INVESTIGATION IT WAS INITIALLY FOUND THAT THE INTAKE AND EXHAUST ROCKER ARMS WERE DAMAGED. THE CAP WAS SLIGHTLY DAMAGED. THE ROCKER COVER WAS PUNCTURED AND THE INTAKE PUSHROD WAS BENT. FURTHER INVESTIGATION REVEALED DAMAGE ON THE CAM SHAFT LOBE.

(AUS) NO4 CYLINDER EXHAUST VALVE SEAT SEPARATED FROM CYLINDER. NO2 CYLINDER EXHAUST VALVE AND VALVE GUIDE UNSERVICEABLE. NO2 CYLINDER HEAD EXTENSIVELY CRACKED.

(AUS) ALL SIX CYLINDERS FOUND TO HAVE EXCESSIVE WEAR TO PISTONS, RINGS AND VALVE TRAIN INCONSISTANT WITH TIME SINCE OVERHAUL - SUSPECTCAUSED BY UNREPORTED ENGINE OVERSPEED

Parts most often named Shaft (2) · Shaft Veny (1) · Gearbox (1) · Bearing (1)

(CAN) UPON WALK AROUND OIL IN GEARBOX LOOKED DIRTY, OIL WAS DRAINED AND METAL WAS FOUND ON MAGNETIC PLUG, TAIL ROTOR GEARBOX WAS REMOVED FROM [S/N removed] AND OH ONE INSTALLED AND ACFT WAS RELEASED. MORE INFO WILL BE POSTED AS THE GEARBOX IS DISASSEMBLED.

(CAN) DURING ROUTINE 100 HR INSPECTION THE OIL WAS FOUND TO BE DARKER IN COLOR THAN NORMAL, AFTER CLOSER INSPECTION AND CHECKING FOR STEEL WITH A MAGNET THE DARKNESS IN COLOR WAS ATTRIBUTED TO METAL CONTAMINATION IN THE OIL SO FINE THAT IT LOOKED LIKE METALLIC PAINT. THE GEARBOX IS IN FOR TEARDOWN AND WILL ADVISE THE FINDINGS AFTER INSPECTION. (TC NR 20070419004)

TAIL ROTOR GEARBOX PINION SHAFT WORN AND INCORRECT PART. BELL 47 SI 428 CALLED FOR REPLACEMENT OF P/N 47-645-205-1 WITH P/N 47-645-205-3 SHAFT.

Parts most often named Lockwasher (1) · Crankshaft (1) · Gear (1) · Stud (1)

MAGNETO IDLER GEAR SHAFT BROKE, THE BREAK WAS CAUSED BY A WORN BUSHING ON THE GEAR/SHAFT P/N'S 76091 & 76283 THAT DRIVES IT. THIS IS THE SECOND TIME THIS SHAFT BROKE. TOTAL TIME SINCE OVERHAUL 230 HOURS.

CRACK-LIKE INDICATION DETECTED BETWEEN WELD AND HOLE 2 AND END OF ROD. FLUORESCENT PENETRANT INSPECTION AND MT INSPECTION USED.

(AUS) CRANKSHAFT CRACKED. CRACK RAN THROUGH THE OIL GALLERY, ACROSS THE THRUST FACE AND THROUGH THE OPPOSITE OIL GALLERY. CRACK EXTENDS THROUGH ALMOST 60% OF THE CIRCUMFERENCE OF BEARING JOURNALSURFACE.

Parts most often named Bearing (3) · Spring (1) · Clutch (1)

AIRCRAFT IN CRUISE AT 300 FT AGL CLUTCH SLIPPED AUTOROTATION PERFORMED DISASSEMBLED FOUND PARTIAL CONTACT OF CLUTCH/DRUM FACE. DRUM AT MAX LIMITS. MORE CAUTIOUS MEASUREMENT DURING OVERHAUL AND REQUIRED INSPECTION.

(AUS) MAIN ROTOR TRANSMISSION DRIVE FLANGE SHEAR SCREWS DISTORTED - SUSPECT DUE TO SLIPPAGE OF THE FREEWHEEL UNIT DUE TO FITMENT OF UNDERSIZE BEARING ROLLERS AND SUBSEQUENT SHOCK LOADING DURING RE-ENGAGEMENT - SEE ALSO MDR 96/0435 AND MDR 96/0341

AIRCRAFT EXPERIENCED SLOW ROTOR ENGAGEMENT AT START-UP. TENSION DIMENSIONS AND FINISH OF FREEWHEEL SPRINGS VARY GREATLY. SUBMITTER SUGGESTS BELL NEEDS TO IMPROVE QUALITY OF SPRINGS.

Parts most often named Idler Gear (1) · Magneto (1) · Capacitor (1) · Gear (1)

LOADED HELICOPTER SAFELY LANDED AFTER MAGNETO FAILURE. WIRE FROM CAPACITOR TO POINTS OPEN WITHIN INSULATION. NO VISIBLE DAMAGE, HOWEVER, MOVEMENT OF WIRE AGAINST CAPACITOR RESTORES CONTACT. YOU CAN FEEL IT. OPEN LOCATED WHERE WIRE ENTERS CAPACITOR. NO RECOMMENDATIONS. (K)

MAGNETO DRIVE IDLER GEAR SHAFT FAILED CAUSING BOTH MAGNETOS TO BECOME INOPERATIVE AND THE ENGINE FAILED. THE FAILURE APPEARED TO ORIGINATE AT THE OIL HOLE. TOTAL TIME ON THE ENGINE WAS 4600 HOURS AND TOTAL TIME ON THE PART PROBABLY WAS 4600 HOURS AND THE ENGINE TSO 220 HOURS. THERE WAS NO VERFICATION THE PART WAS MAGNAFLUX AT OVERHAUL. RECOMMEND FOLLOWING THE MANUFACTURERS RECOMMENDATION AND MAGNAFLUX ALL STEEL PARTS. FURTHER THE OIL HOLE DID NOT APPEAR TO HAVE ADEQUETE RELIEF WHEN MANUFACTURED.

AIRCRAFT LANDED AT REMOTE FIELD LOCATION ON ISLAND. SEVERAL HOURS LATER, AIRCRAFT STARTED. RIGHT MAGNETO COMPLETELY FAILED. ON RPM MAG CHECK, MAGNETO REMOVED AND TAKEN APART. NYLON DISTRIBUTOR GEAR LOST 3 TEETH. GEAR USED WAS NOT NEW, CHECKED WITH TELEDYNE CONTINENTAL. THEY CONFIRMED DISTRIBUTOR GEARS ARE ROUTINELY REUSED. SINCE THERE IS NO WAY TO ZYGLO OR MAGNAFLUX NYLON DISTRIBUTOR GEARS, SUBMITTER RECOMMENDED ROUTINE REPLACEMENT OF ALL DISTRIBUTOR GEARS AT FACTORY OVERHAUL. (X)

Parts most often named Driveshaft (1) · Bearing (1) · Universal Joint (1) · Drive Shaft (1)

BEARING FAILURE IN UNIVERSAL JOINT. NOTICED BY VIBRATION IN FLIGHT AND CLICKING SOUND ON SHUT DOWN. INVESTIGATION SHOWED OFF SET IN UNIVERSAL JOINT AND EXCESSIVE RUN OUT OF AFT TAIL ROTOR SHAFT. REPLACED UNIVERSAL JOINT, CHECKED RUN OUT, AFT SHAFT AND EXTERIOR SHAFT. AIRCRAFT RETURNED FOR [S/N removed].

(AUS) TAIL ROTOR DRIVE SHAFT AND BEARINGS OUT OF ALIGNMENT. GREASE DISCOLOURED AT NR 1, NR 2, NR 7, AND NR 8 BEARINGS. ALL BEARINGS SHOWED SIGNS OF HEAVY WEAR.